Severity scoring in the ICU: a review

Background: Patients in the intensive care unit (ICU) require huge resources because of the dysfunction of several of their vital organs. The heterogeneity and complexity of the ICU patient have generated interest in systems able to measure severity of illness as a method of predicting outcome, comparing quality-of-care and stratification for clinical trials. Methods: By searching Medline and EMBASE for publications describing scoring systems in the ICU, the most frequently used systems, defined as resulting in more than 50 references, are included in this review. Scoring systems belong to one of four classes prognostic, single-organ failure, trauma scores and organ dysfunction (OD). The different systems are described and discussed. Results: Three different prognostic scoring systems, including several versions, four single OD scores and three OD scores, were included in this review. Conclusion: Different forms of scoring systems are frequently used in the ICU. They have become a necessary tool to describe ICU populations and to explain differences in mortality. As there are several pitfalls related to the interpretation of the numbers supplied by the systems, they should not be used without knowledge on the science of severity scoring.